1. Field of the Invention
This invention relates to a crutch assembly which may have its longitudinal dimension selectively increased or decreased to accommodate different heights or elevations of walking surfaces over which a user of the crutch may travel.
2. Description of the Prior Art
Existence in the prior art of crutch structures which are capable of having their length adjusted are well known in the art. Typically, such known crutch structures are built primarily to accommodate use by people of varying heights. Alternately, there exists in the prior art crutch structures which are substantially collapsible for purposes of storage and ease in transportation when not in use.
U.S. Pat. No. 4,917,126 to Ellmore is representative of at least one type of the above-described prior art crutches. The structure disclosed in this patent relates to a stowable crutch including a body consisting of a first and second tube secured to each other and a third tube being slidably mounted within the first tube. A fourth tube to which an underarm support is secured is slidably mounted within the second tube. The various first, second, third and fourth tubes are all relatively adjustable so as to selectively dispose the crutch assembly of this invention between an extended, operative position and a collapsed, stowable position.
The patent to Chen, U.S. Pat. No. 4,865,065 is directed to an improved height adjustable crutch having a central carrier member telescopingly received within an extendable leg member. The extendable member is adjustable by sliding movement and fixed into an operative position by the provision of a biasing spring or locking devise to interconnect fixed and sliding members.
The U.S. Pat. No. 3,417,765 to Slater, et al., discloses a telescoping crutch having an upper support portion designed to fit beneath the arm of the user and being spring biased and accordingly outwardly adjustable. Similarly, a lower leg portion is outwardly extendable and adjustable. Both the longitudinally adjustable members are extendable and fixed into an operative position by the existence of hand manipulated connectors.
U.S. Pat. Nos. 2,674,253 to Hopkins and 3,157,189 to Farnham are both directed to a "automatically" adjustable length crutches in the sense that the length of the crutch may be adjusted essentially while being used and while in its generally operable position without necessitating the user to physically manipulate the parts relative to one another. To the contrary, Hopkins discloses a spring biased lower leg member which, upon actuation of a trigger, serves to activate a plurality of elongated lengths or actuating rods externally mounted. Each of the lengths are connected to a stop member cooperating with an externally located gear extending along the length of the lower extendable leg. Manipulation of the trigger mechanism serves to operate the rather complicated linkage and break or stop members causing the relative movement of the lower leg portion to the remainder of the crutch. While operable for its intended function, the Hopkins structure appears to be overly complicated, and obviously has many of its working components externally accessible, thereby rendering them accessible for inadvertent damage. Further, the complication of the Hopkins structure renders it questionable for commercial application.
Farnham is extendable through operation of an electric motor and, accordingly, is questionable from an expense standpoint and also renders such a crutch structure possibly too heavy or inconvenient for use in commercial application.